Pollen interference between rare and common species

The mechanisms underlying plant species distribution and abundance have
been long studied in ecology. However, the role of heterospecific pollen
interference in shaping these patterns remains unaddressed. Species
distribution and abundance are important factors determining whether a
species is endangered or not, thus understanding the impact of
heterospecific pollen interference on rare species could help to inform
conservation strategies aimed at preserving plant communities. In this
study, we conducted a multispecies experiment using eight co-occurring and
co-flowering plant species with varying rarity levels in Switzerland. We
performed hand-pollination experiments between all species pairs and
measured seed set (whether a flower produces seed) and seed number (number
of seeds per flower) as outcomes. We looked at the effects of species
rarity status, species self-compatibility and recipient-donor relatedness
on heterospecific pollen interference. Contrary to expectations, neither
seed set nor seed number were affected by heterospecific pollen
deposition. Self-compatible species had a higher seed set probability, but
this was independent from species rarity. Lastly, rare species showed a
decrease in heterospecific pollen interference with more distantly related
pollen donors when these were rare as well. In our study setting,
heterospecific pollen interference seems to have only minor effects on
seed set and seed number, and consequently on recruitment. Thus,
heterospecific pollen interference seems to play only a minor role in
shaping plant species distribution and abundance. Nevertheless, the higher
impact of heterospecific pollen deposition for rare and closely related
species might need further investigation for both in-situ and ex-situ
conservation strategies.